<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>盒子模型</title>
    <style>
        #d1{
            width: 500px;
            height: 500px;
            border: 1px solid #000;
        }
        #d2{
            width: 200px;
            height:200px;
            background: pink;
        }
        #d3{
            width: 200px;
            height: 200px;
            background: blue;
            margin: 4px;
            padding: 2px;
            border: 2px solid #000;
        }
    </style>
</head>
<body>
    <div id="d1">
        <div id="d2"></div>
        <div id="d3"></div>
    </div>
</body>
</html>